Genetic science applied to historic prints

Technique could help date Rembrandt and Shakespeare works

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These images are close-ups of a half-inch-wide (centimeter-wide) section of prints from two editions of an Italian Renaissance book by Porcacchi. The left image is from a 1576 edition, the right from 1604. The comparison illustrates time-dependent image fading, useful for dating books and prints.

The fundamentals of genetic science may help date centuries-old works by Shakespeare and Rembrandt.

It could be a new benchmark for the science world's oddest crossover research.

The newly announced technique, which proposes to assign years to a slew of previously undated books and art, applies the same thinking behind genetic mutation studies to determine deterioration rates of the devices used in early printing. It was thought up, naturally, by a biologist.

"My print clock, just like the ones used in geology and biology, looks at changes that appear to occur randomly," explained Blair Hedges, Penn State biologist and the project's primary researcher. "The only difference here is that the changes are occurring in wood and copper."

How it works
Before methods were modernized in the mid-19th century, printers used either wood blocks or copper plates to transfer literature and art to paper. To save money, these plates were reused over several decades to produce multiple editions of the same print.

The blocks and plates would wear down over time, affecting the quality of copies printed in the later stages of a plate's run. In the case of wood blocks, Hedges said, this created a noticeable increase in the number of line breaks in a print, while copper plates showed age in images that became gradually more faded.

Working first with a collection of 2,674 Renaissance prints and maps, Hedges used image-analysis software to note the quality changes and record them as statistical data.

"Studying a large enough number of prints showed that the blocks and plates actually deteriorated at a regular rate," he told LiveScience. "Using just a few known dates for calibration, you can get a pretty accurate estimate of time elapsed between prints."

Hedges applied his theory to a 16th-century atlas created with wood blocks and came up with a date just two months shy of another independent test.

The full scope of the scientist's research will be published in the journal Proceedings of the Royal Society A: Mathematical, Physical, and Engineering Sciences.

Obvious method
While the deterioration he spotted in the prints is visible to the naked eye and could have tipped off book experts to the same discovery at any time, Hedges believes his biological background gave him the upper hand.

"It is probably counterintuitive for most people that such random noise (breaks in lines on prints) could be used as a clock," he said. "The only reason it occurred to me is because I use this same principle in genetics for dating the origin of species."

Despite its unorthodox provenance, historians concerned with early books think the relatively simple system could completely replace most other dating techniques in use today. Lucky for them, next up on Hedges' print clock research schedule are a few very recognizable names.

"Many prints by Rembrandt are undated, and I would like to try the method on them," he noted, as well as "Shakespeare's undated plays 'Hamlet' and 'Romeo and Juliet.'"